• first of all I must say that my intent here is NOT to tread on anyone's toes

I just don't like when an idea, not founded on reality, begins to spread and everyone thinks it's the truth, while the facts say something else

• the background:

many users in this and other forums reported the same "feeling" that something is wrong when using the default Input Settings which means selecting the same signal for input 1 and 2 (I'll refer to this as "guitar/same" o "both inputs active"):

according to them, this setting introduces some artifact which I'll call for simplicity "the input settings phase issue"

as a consequence they say that by choosing guitar/variax (therefore "disabling" input 2) you get a better tone

(of course if you use a variax you must "translate" what you read, the point is: if you are using only one instrument, should you choose its input for Input-1 and "same" for Input-2 or not?)

• I never read more than personal opinions on this matter and no "scientific" tests and of course simply switching between one or two inputs in the same patch is not even to take into consideration due to gain differences

so I decided to run those tests by myself

• even before testing I must say that, if the phase issue between input-1 and 2 was true, then it should be ascribed to a serious bug in the POD HD signal routing

"both inputs active" is even the default setting so it should work as expected

• if you're interested in the POD HD signal routing and to take full advantage of the possibilities of this machine, please take a look at these routing schematics I built months ago based on many tests:

as I already wrote, this does NOT mean that using only one input (Guitar/Variax) is wrong,

on the contrary, it is perfectly reasonable if you want cleaner tones:

it gives exactly the same result as adding a fixed volume pedal at -6dB, but it's better, because you don't waste an fx block!

in the same way simply no one can saythat using both inputs is wrong or that it's causing problems on its own (unless he/she proves it);

on the contrary, if you want to use a dual amp setup and you choose only one input (Guitar/Variax) then you have to waste an fx block (e.g. noise gate 100%-0%) to send the signal to both paths!

This doesn't make sense to me at all.

• I did the tests with a BC Rich Mockinbird with a DiMarzio Super Distortion on the bridge position, mounting GHS Boomers 11-50: not exactly a quiet signal...

and I didn't even have to insert the input pad of the pod;

so for me no clipping is caused by the use of both inputs alone at least for the effects I used in the tests

of course, for example, the studio eq and the tube comp have a relatively low clipping threshold with respect to the POD internal routing BUT it is a simulation of an analog clipping so it's an intended effect!

and again I've got nothing against the usage of the single input if you want to put one of those effects as the first and want it to be cleaner but please then do not crank the output of the effect or you'll be back to the start!

• last but not least, please if you are confused by the routing do not think that you have to use the "path A only" solution (putting everything in path A, center its pan and mute path B ),

you will get exactly the same tone and simplicity by using the defaults

to be more detailed:

- start from the default new tone (maybe switch the inputs to guitar/same jut to avoid any possible noise from other inputs)

- use the amp in the default position (pre split)

- if you don't need the parallel A/B paths simply do not touch them or the mixer

- put the pre effects like distortion in the pre path

- put the post effects like reverb in the post path

and you'll be perfectly ok

this should be written in the manuals, and in part is is,

I needed to clarify it

• for those of you who are interested, I created a setlist with the patches I used for testing, so that you can hear for yourself;

in a note inside the zip file, there are the descriptions of the patches and of the tests I did

• some amplifiers/fx models can have a slightly different sound thanks to an attenuation to the signal sent to them independently from their drive pot position (maybe because there is some pre-drive-pot circuit ?!? thanks to gckelloch for the idea)

this attenuation can be obtained with the "single input" setting only if your amp/fx is in the pre path, otherwise you need a workaround

First, thank you for putting in the time and effort to present your findings and offer the patches that you used for testing.

Second, why have we not heard from a Line 6 engineer, who has direct knowledge of this program, explain exactly how the inputs and associated settings work?

EDIT: Maybe I am wrong about my comment above, It is defined in the advanced manual.

About Source Input Signal Routing:

2•7

It is important to note how POD HD500X actually routes Source Inputs 1 and 2 through Amp & FX Blocks that are positioned “Pre” position. The following behaviors apply:

In a configuration with no Amp or FX Blocks in Pre, Input 1 is fed only to Path A and Input 2 only to Path B. Therefore, this is the best configuration if you want to retain discrete Input Sources into Paths A & B.

Placing an Amp Block or an active mono FX Model in Pre results in a “mix-down” of Input Sources 1 & 2, feeding the same, combined signal into each Path A & B.

Placing a Stereo FX Model in Pre results in the left channel FX output being fed to Path A and its right output to Path B.*

The Mixer Block’s Volume and Pan options provide independent control for Path A & B outputs before they are fed through any Blocks positioned “Post” the Mixer.

By setting Input 2 to “Same,” this effectively routes your Input Source to both stereo Paths A & B (which is how you can feed one guitar input into two Amp Models and/or parallel FX, for example).

First, thank you for putting in the time and effort to present your findings and offer the patches that you used for testing.

Second, why have we not heard from a Line 6 engineer, who has direct knowledge of this program, explain exactly how the inputs and associated settings work?

EDIT: Maybe I am wrong about my comment above, It is defined in the advanced manual.

About Source Input Signal Routing:

2•7

It is important to note how POD HD500X actually routes Source Inputs 1 and 2 through Amp & FX Blocks that are positioned “Pre” position. The following behaviors apply:

In a configuration with no Amp or FX Blocks in Pre, Input 1 is fed only to Path A and Input 2 only to Path B. Therefore, this is the best configuration if you want to retain discrete Input Sources into Paths A & B.

Placing an Amp Block or an active mono FX Model in Pre results in a “mix-down” of Input Sources 1 & 2, feeding the same, combined signal into each Path A & B.

Placing a Stereo FX Model in Pre results in the left channel FX output being fed to Path A and its right output to Path B.*

The Mixer Block’s Volume and Pan options provide independent control for Path A & B outputs before they are fed through any Blocks positioned “Post” the Mixer.

By setting Input 2 to “Same,” this effectively routes your Input Source to both stereo Paths A & B (which is how you can feed one guitar input into two Amp Models and/or parallel FX, for example).

thanks to you RIblues for reading, about your question

1- I asked for a Line 6 official statement more than a year ago by way of a public request on the (old) forum, a support ticket and personal messages to many line 6 so called experts: none of them ever replied, ever

2- Line 6 engineers do not write (or read?) on this forum

3- nothing of what I wrote here or in my routing schematics post is in any contraddiction with the manuals,

I'm simply explaining in more detail and giving MORE information about the pod routing

I am sure of what I wrote so I personally won't ask again for confirmation

p.s.

the unofficial czech language translator of the manuals (he works wor the local distributor, not Line 6) asked me to use my routings in his translation

I still think it's possible that using both inputs can overdrive the inputs especially if you have a guitar with more than typical output signal. This can lead to clipping and nasty sound. Guitar outputs vary a lot.

Good to have this info in one place. The inputs must be before the dual A/D converter, right? Yes, many factors influence guitar output, but setting the inputs the same shouldn't make a difference to the A/D, because each side of the converter gets the same signal level. So, if you are not clipping the inputs, retaining unity gain throughout should not cause internal clipping.

It should be noted that centering the Mixer block "pans" with identical signals on both input paths does boost the signal by 6dB, and could clip the D/A converters. Even setting model block outputs up too high might clip the D/A. That's why it's important to achieve unity gain throughout the entire path. It makes sense to start with a clean uncompressed and full sounding preset - making sure it never clips the D/A - as a reference to adjust loudness levels for all other presets. Make sense to everyone?

I still think it's possible that using both inputs can overdrive the inputs especially if you have a guitar with more than typical output signal. This can lead to clipping and nasty sound. Guitar outputs vary a lot.

with the input settings you can clip some kind of fx blocks not the inputs

from my tests the pod itself (new tone) whithout the input pad clips at +10.5dBu with or without the second input active

with the pad active it clips at +15.5dBu with or without the second input active

if your guitar has such a hi-output to clip the input circuit of the pod (even with the pad active) there is no input setting to help you

Great topic and I too have been bouncing between the settings and trying to decide which was "correct". After reading everything so far, I picked up on the part in the HD Edit guide that says:

The POD HD500 Source Input 1 is fed through Path A, and Source Input 2 is fed through Path B, unless a mono FX Model is inserted in the Pre position, which down-mixes the two input sources to mono and feeds them both equally into Paths A and B. (See the Input Selectors section on page 2•2.) Note that you can move all FX and Amp Blocks out of these Paths completely, but the Paths always exist, and your Source Inputs are always fed through them, and thus, through the Mixer Block.

This backs up what was posted above from the Advanced Guide. So it seems the purpose for the Input 2 "Same" setting is to provide a signal to path B. Based on all this, I created a patch to test this out. I made a dual amp patch with nothing in the Pre section and used Vol blocks set to zero to mute the amps when activated with FS 2 or 3. I put a mono Noise Gate in the Post section for use during testing.

1. With inputs set to Guitar and Same - both amps are working together. When I mute Path A, signal continues for Path B. When I mute Path B, signal continues for Path A.

2. With inputs set to Guitar and Variax - only Path A is heard. When I mute Path A, there is no signal from Path B. Path A volume is the same as in step 1.

- this confirms that the signal from Input 1 is ONLY fed to Path A and Input 2 is fed to Path B.

Now move the Noise Gate to the Pre position, changing nothing else.

3. With inputs set to Guitar and Same - both amps are working together. When I mute Path A, signal continues for Path B. When I mute Path B, signal continues for Path A. Volume remains the same as steps 1 and 2.

4. With inputs set to Guitar and Variax - both amps are working together. When I mute Path A, signal continues for Path B. When I mute Path B, signal continues for Path A. Volume is reduced for both paths.

Conclusion:

- I believe the standard signal strength from the above tests is the higher one since that is what is being passed directly to each path in step 1 as POD default.

- Step 3 showed that the mixed down mono signal from both inputs is no hotter or different than the individual signal being fed to each path in step 1.

- Step 4 showed that the signal passed by the mono block without the second input is weaker than the signal in step 1, 2 or 3.

While there still may be no "correct" configuration, for me at least, step 4 lacked body and fullness as heard in the other steps. Contrary to my previous misunderstanding, the signal from "both" inputs is no hotter than the individual signal passed to the channels in step 1. In fact the lowered signal is caused solely as a result of the mix down within the mono FX block with only one input feed. I am going back to using the Guitar/Same input configuration unless I specifically need a lower input signal.

Please try it out for yourself and tell me if you find the same results... Merry Christmas!

PS - as it states in the manual, only a MONO block in the PRE section will perform the mix down and feed both paths. An empty block or a stereo block such as a Wah will NOT feed path B unless Input 2 is set to "Same".

0

Quit complaining and DO something or help somebody with their issues...

The question still remains whether driving the amp models with the output of an FX block sounds any different than turning up the amp gain. I suspect it does...but maybe not for certain models of amps with actual master volumes? Line 6 should fill us all in on this...unless maybe they figure answer is obvious?

Thanks, hurgh. People should really experiment with those preamp gain nuances before complaining that the amp sound is either too brittle or whimpy. Of course, it's not really like using the guitar volume with passive pickups, because unless you have a specifically designed "treble" bleed circuit in accordance with the external capacitance load, the highs will in most cases be attenuated as you turn down the guitar volume.

I went back and tested my PODHD switching back and forth between Guitar/Same and Guitar/Mic - I have the Desktop version. My tone is a Noise Gate, Tube Compressor, Angel-Pre, Stereo Delay, Stereo Reverb.

And when I switch it to Guitar/Same it is slightly louder, and I mean very slight. Actually the only differance I hear is when the tone starts to fade and I switch it from Guitar/Mic to Guitar/Same. During normal play I can't tell at all. But this could be due to the Compressor.

I'm going to do some more testing but at high volumes to see if feedback is more of a problem and of course to see if there's any differance in tone, feel, noise, etc.

what you describe is exactly what should happen with that setup. The mono noise gate is looking for two inputs, 1 and 2, summing them and mixing down to feed to paths A and B. With only one input the resultant mixed down signal is weaker than it would be with guitar/same (the output is actually weaker than the input). Not that there is anything wrong with that, just that we know why it is happening. I prefer the full signal provided with guitar/same.

0

Quit complaining and DO something or help somebody with their issues...

with my tests posted above I demonstrated that attenuating the input signal with a volume pedal by 6dB or with the "single input" setting gives exactly the same result, ...

...now a QUESTION arises:

is it possible to compensate the difference between single input and dual input by just using the drive pot on the amplifiers?

to answer, I did some other tests starting from a guitar/guitar patch (A) duplicating it and changing to guitar/variax (B ) and then setting the right amount of drive by ear and then comparing the two patches in two ways:

playing guitar and sending a looped riff, I can hear subtle differences on a couple of amps where I can't find the right value for the drive (but the difference is not clearly better/worst it's just a bit different)

looking at the FFT's those same amps have one or two different harmonics levels between A and B:

soldano

jcm800 + screamer

plexi + boost comp (the plexi alone doesn't have this problem so the boost comp is clearly the culprit)

another pair have micro differences in a couple of harmonics (and I can't hear the difference):

twin

vox ac30

the rest looks and sounds the same

jtm45

plexi

park 75

mesa

bear in mind that the differences are tiny (except for the soldano, the "worst": 10db on the 3rd harmonic and 3dB on the 2nd) and that I wouldn't choose one or the other (A/B) based on these tests (you have to play with the sound in context to chose what you like more),

but I can confirm that there are some little differences.

I hope this work of mine at least can give you a method to build two identical patches changing only the input setting and the drive value to compare them and, in each case, choose which sounds best to you

here you are the FFT's (where red is A and yellow is B and the white horizontal lines are every 10dB)

• choosing a single input is ONLY attenuating the input signal level by 6dB (no phase or other issues)

(I also re-tested the patches I uploaded with my original post with the sine wave/FFT method and all the A/B couples are identical: this confirms one more time that the single input is just an attenuation of 6dB at the input)

• some amplifiers/fx models can have a slightly different sound thanks to this attenuated signal independently from their drive pot position (maybe because there is some pre-drive-pot circuit ?!? thanks to gckelloch for the idea)

so bear in mind that if someone wants the attenuated signal to be sent to his amp and wants to put it on A or B path, he needs another way to attenuate the signal (since he doesn't have the possibility to attenuate with the input settings choice):

he can switch the pad in, he can add a fixed volume pedal @71% before the amp or he can activate only one input and then add a noise gate (100/0) which acts as a splitter in the PRE path and then put the amps in A and/or B path (this is how meambobbo does it); (using a studio eq as an attenuator is NOT a good idea since it has its sound, even at unity and it also sucks CPU power)

• overdrive and distortion fx blocks send a higher level to the amp than the direct guitar, so if you don't like the sound of a specific distortion block into a specific amp, it could be a good idea to lower the distotion block output volume instead of lowering the amp's drive

CONCLUSION

So, if the routing you use allows you to do it, it's worth comparing the single input vs the dual input (the comparison must be made, as I did, with two identical patches changing only the input setting and the drive value);

if your routing doesn't allow you to try different input settings (e.g. you use two instruments on two separate paths) you can also try a fixed volume pedal at 71% before your amp/distortion pedal

I went back and tested my PODHD switching back and forth between Guitar/Same and Guitar/Mic - I have the Desktop version. My tone is a Noise Gate, Tube Compressor, Angel-Pre, Stereo Delay, Stereo Reverb.

And when I switch it to Guitar/Same it is slightly louder, and I mean very slight. Actually the only differance I hear is when the tone starts to fade and I switch it from Guitar/Mic to Guitar/Same. During normal play I can't tell at all. But this could be due to the Compressor.

I'm going to do some more testing but at high volumes to see if feedback is more of a problem and of course to see if there's any differance in tone, feel, noise, etc.

you only hear a tiny difference in level in the tails of your notes because both the tube comp and the distortion of the amp do compress the sound a lot

It makes sense that at least the Soldano would have a higher 3rd harmonic level when the front is pushed harder than from within the preamp with the Drive knob after the first gain stage. The models of older amps may not have included that aspect in the modeling, or the volume knobs on those amps simply drive from the first preamp stage.

I'm surprised the Mesa does, though. I'm not sure running a 1kHz tone through the amp really tells the whole story. I think you'd need to run some sort of noise impulses at different levels to do an accurate response test. The preamp might recover differently with various transients depending on how it's driven. There may be impulse sets specifically for this type of test that you can download somewhere. You'd also want the amp DEP Master as low as possible so it doesn't alter the results, and no speaker cab, mic or FX. Ether way, thanks for checking it out pera.

I went back and tested my high gain tone at normal live playing volumes - which is loud. With the input set on Guitar/Same I had some occasional squeeling feedback that isn't there with the inputs set at Guitar/Mic (I have the PODHD Desktop). It seemed like the signal was almost too hot but didn't notice any clipping. Probably some adjustments elsewhere could have fixed it, but setting the inputs to Guitar/Mic made everything work fine.

Didn't notice any differance in tone or feel. I'm using the Angel Pre into the FX return of a Marshall.

Setting the inputs is something I believe people should be aware of and try differant combinations. Sounds like differant amp models or setup combinations will have varying results. But knowing the input settings can have an effect is good to know.

My experience with my 500x...
if you run left and right outputs into any digital interface - essentially mono signals you get phasing.
if you run left right xlrs out and create a stereo track in your daw of choice and track multiple guitars the phasing issue does not seem to be a problem.
I ran into this finishing up tracking holes on a record i am working on.